title: Diagnostic value of metabolic tumor volume assessed by 18F-FDG PET/CT added to SUVmax for characterization of thyroid 18F-FDG incidentaloma.
abstract: BACKGROUND
  The objective of the study was to investigate whether metabolic tumor volume (MTV) measured by fluorine-18 fluorodeoxyglucose (F-FDG) PET/computed tomography (PET/CT) after stratification of serum thyroid stimulating hormone (TSH) levels could predict malignancy in patients with thyroid F-FDG incidentaloma.
  
  
  METHODS
  A total 262 patients with focal thyroid F-FDG incidentaloma undergoing cancer evaluation for nonthyroid cancer or a health checkup were enrolled in this study. We retrospectively evaluated the relationship of the maximum standardized uptake value (SUVmax) and MTV in the prediction of malignant thyroid F-FDG incidentaloma.
  
  
  RESULTS
  The prevalence of malignancy was 20.9% (37/177). Malignant thyroid incidentaloma had a statistically significant higher value of SUVmax (malignant: median 4.6, range 1.9-34.9; benign: median 4.1, range 0-28; P=0.030). The value of MTV4 in malignant thyroid incidentaloma was significantly higher than that of benign thyroid incidentaloma (malignant: median 0.16, range 0.02-1.19; benign: median 0.10, range 0-0.65; P=0.032). However, the values of MTV3.5, MTV3, and MTV2.5 did not differ significantly between the groups. After stratification of serum TSH levels (an SUVmax>5 was used as the cutoff point) the sensitivity and specificity for prediction of malignancy were found to be 61.1% [95% confidence interval (CI): 35.7-82.7%] and 68.7% (95% CI: 56.2-79.4%), respectively. The area under the curve (AUC) was 0.655 (95% CI: 0.545-0.755; P=0.0239). When MTV4 greater than 0.07 cm was used as the cutoff point, the sensitivity and specificity for prediction of malignancy were 81.2% (95% CI: 54.4-96.0%) and 50.0% (95% CI: 37.0-63.0%), respectively. The AUC was 0.650 (95% CI: 0.534-0.755; P=0.0451). On comparison receiver operating characteristic curve analysis, no significant difference was found between SUVmax and MTV4 in the prediction of thyroid carcinoma (P=0.4346). However, a combination of SUVmax and MTV4 resulted in an AUC of 0.669 (95% CI: 0.554-0.772; P=0.0183).
  
  
  CONCLUSIONS
  The SUVmax and MTV4 measured by F-FDG PET/CT after stratification of serum TSH levels could predict thyroid cancer in patients with thyroid F-FDG incidentaloma. A combination of SUVmax and MTV4 may be more useful for the differentiation of malignant from benign thyroid incidentaloma.
authors.affiliation: Department of Internal Medicine, Division of Endocrinology and Metabolism, Pusan National University Hospital, Busan, Korea.
authors.forename: Bo Hyun
authors.initials: BH
authors.lastname: Kim
authors.forename: Seong-Jang
authors.initials: SJ
authors.lastname: Kim
authors.forename: Heeyoung
authors.initials: H
authors.lastname: Kim
authors.forename: Yun Kyung
authors.initials: YK
authors.lastname: Jeon
authors.forename: Sang Soo
authors.initials: SS
authors.lastname: Kim
authors.forename: In Joo
authors.initials: IJ
authors.lastname: Kim
authors.forename: Yong Ki
authors.initials: YK
authors.lastname: Kim
mesh_terms: D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D033162:Incidental Findings; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D013964:Thyroid Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000378:metabolism* / Q000473:pathology; D013972:Thyrotropin / Q000097:blood; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden
chemical_list: D019788:Fluorodeoxyglucose F18; D013972:Thyrotropin